In a wide variety of industries, including processing and manufacturing facilities, exhaust gas streams containing harmful volatile organic compounds (VOC's) are generated. Representative industries include graphic arts; printing; textiles; metal coating, including can, coil and film coating; production of magnetic tape; metal finishing; all varieties of chemical and petrochemical processes; resin and plastics production, etc. Because strict compliance with EPA guidelines and other regulations on exhaust gas stream composition is paramount, it is necessary to adequately treat exhaust gas streams containing VOC's to reduce the presence of the VOC's to acceptable levels. Under appropriate conditions, typical VOC's generated in the industries identified above, and others, can be oxidized and converted to carbon dioxide (CO.sub.2) and water vapor.
Systems which catalytically incinerate (oxidize) VOC's are known in the art. Stelter & Brinck, Inc. of Harrison, Ohio, is one designer and manufacturer of such systems. In a typical catalytic incineration system, the VOC's are supplied to the system and conveyed therethrough by means of a blower. Since catalytic oxidation of VOC's typically occurs only at elevated temperatures, on the order of 550.degree. F. and higher, it is necessary to heat the VOC's. This is generally accomplished by means of a flame burner which heats the air stream containing the VOC's to a sufficiently elevated temperature for oxidation. The VOC's and combustion air are then contacted with a suitable catalyst which initiates the oxidation reaction; this reaction produces CO.sub.2 and water vapor as exhaust. Since the oxidation reaction is exothermic (i.e., it generates heat), it has been recognized that the overall energy efficiency of the system can be improved by utilizing at least one heat exchanger to recover the latent heat from the hot exhaust vapors produced in the oxidation reaction and transferring that heat to the incoming VOC's, to preheat them.
One important consideration in the design of catalytic incinerators is obtaining temperature uniformity of the gases contacting the catalyst. Temperature uniformity is important to ensure substantially complete oxidation of the VOC's. Accomplishing this uniformity has proved to be a difficult task in the past. Additionally, known catalytic incinerators typically had to be fairly large to accommodate a heat exchanger that transfers heat to the VOC's with a reasonable degree of efficiency. Another drawback of known catalytic incinerators is their susceptibility to thermal stresses, particularly in the area of the heat exchanger.
As will be described hereinbelow, the present invention is believed to overcome the various drawbacks associated with known catalytic incinerators, while providing all the advantages and flexibility of such known systems.